These Thick and Chewy Monster Cookies are loaded with peanut butter, oats, M&M’s and chocolate chips. They’re a cross between a chewy oatmeal chocolate chip cookie, and a peanut butter cookie, and they’re sure to be a huge hit with family and friends.

I LOVE making cookies, and since I don’t usually have fresh-baked cookies available on the spot, I like to freeze them for when friends come over or when we just want a little treat.  In my freezer currently are Jumbo Chocolate Chip Cookies, Red Velvet Sandwich Cookies, and Chewy Pumpkin Chocolate Chip Cookies.  Who wants to come over?!

Monster cookies with m&m's on a wire cooling rack.

Monster Cookies

Don’t ask me to choose a favorite type of cookie because I just wouldn’t be able to! There are too many fun variations. These Monster Cookies are always popular and I love the great texture from the oats and the subtle peanut butter flavor.

Why are they called Monster Cookies?

There’s not an exact answer for why these cookies are called “Monster” Cookies. Some people think it’s because they look like monsters, with their bumpy texture and fun colors. I like to think it’s because they’re stuffed with so much “stuff”, making them the “monster” of all cookies.

Whatever the reason, all Monster Cookies have these ingredients in common: peanut butter, oats, chocolate chips and m&m chocolate candy.

The ingredients for monster cookies including a measuring cup with peanut butter, a small bowl of rolled oats, and a pile of chocolate chips and m&m's.
How to make Monster Cookies:
  • Cream the butter and sugars. Use REAL butter and cream it with the sugar for at least 2-3 minutes until really light and fluffy. This is adding air to the mixture and is the base for the texture we want in our cookies.
  • Mix wet ingredients. Add the peanut butter and mix well. Add egg and vanilla and mix.
  • Measure flour properly and mix dry ingredients. When measuring the flour be sure to fluff it a bit first, allowing air to fill in (like sifting) before you spoon it lightly into the measuring cup. Stir together the flour, oats, salt, baking powder and baking soda. Stir into wet mixture with m&m’s and chocolate chips.
  • Slightly under-bake. Bake at 350, being careful not to over bake the monster cookies. The tops will look just set and they will continue to harden and set up as they cool on the baking sheet.

A bowl full of the dough for monster cookies next to another photo of the cookies rolled into balls on a baking sheet.

How do I keep my cookies from spreading?

During baking, cookies naturally spread, but the key is to make sure they don’t spread too much.  To keep your monster cookies from spreading, be sure to use exact measurements (no guesstimating) and use room temperature ingredients, particularly the butter and eggs.  You can also stop cookies from getting flat by chilling the dough for 15-30 minutes before baking.

Storage and Freezing Instructions:

These cookies will keep well in an air-tight container for 1-2 days, or you can freeze the cookie dough or baked cookies. To freeze them after they’re baked, allow them to cool completely and store them in a freezer safe container for up to 3 months. Freeze cookie dough balls in a freezer safe container and when ready to bake, place the frozen cookie dough on a baking sheet and add 2-4 minutes to the baking time.

Monster cookie on a marble board with a bite taken out of it.

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Monster cookies with m&m's on a wire cooling rack.
Prep 15 mins
Cook 10 mins
Total 25 mins
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  • Preheat oven to 350 degrees F.
  • Cream the butter and sugar together really well—at least 2-3 minutes until light and fluffy.
  • Add peanut butter and mix well. Add egg and vanilla and mix.
  • In a separate mixing bowl stir together the flour (be careful to measure correctly, spooning the flour into a measuring cup, then leveling off), oats, salt, baking powder and baking soda.
  • Add to the wet mixture and mix to combine. Stir in chocolate chips and M&M’s.
  • Bake at 350 degrees for 10-12 minutes, or a little longer if you make them bigger than a 1 inch cookie scoop. Don't over bake--they will look just set. 
  • Remove them from the oven and allow them to cool completely on the pan.


Adapted from our Mrs. Fields chocolate chip cookie recipe.


Calories: 191kcalCarbohydrates: 23gProtein: 3gFat: 9gSaturated Fat: 4gCholesterol: 18mgSodium: 114mgPotassium: 94mgFiber: 1gSugar: 14gVitamin A: 145IUCalcium: 25mgIron: 0.9mg

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About The Author

Lauren Allen

Welcome! I’m Lauren, a mom of four and lover of good food. Here you’ll find easy recipes and weeknight meal ideas made with real ingredients, with step-by-step photos and videos.

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  1. 4 stars
    It is common sense but it does not mention to soften the butter. The cookies did not spread well and the oats in this were hard to chew through, this maybe have been my oats. I also think it could have a little more salt. Overall, I think these are OK, not my favorite, but worth a try.

  2. 4 stars
    This dough was great to work with. I made sure to follow the directions to cream the butter until fluffy and I think that’s key. The cookies looked very underwhelming coming out of the oven, but the taste is good. The recipe made three dozen for me. Unlike some chocolate chip cookie recipes, these monster cookies taste better cool.

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